Harassment - Age, Physical, Psychological, Power, Retaliation, Bullying

My supervisor bullies and uses authority to manipulate and fabricate performance issues. Two coworkers and I notified HR with many examples of bullying issues 5-6 years ago. HR so called “worked” with the supervisor, but she has harbored and retaliated against us with bogus performance issues and low merit increases ever since. Last year, she became verbally hostile at me, standing over me, yelling, and pounding on the desk. She was scary. This has made me very nervous to be around her and has caused me mental and health concerns. She recently gave me a bad performance review which comes with no merit increase for this year and I cannot post out for other jobs in the company. I am 54 yo and 7 months shy of my eligibility for early retirement. She has made statements like “youre not that old yet are you.” She basically capped my pension pay by way of her petty performance issues. I have taken this to HR, reporting the hostile event, her bullying again, and her comments about age and my retirement eligibility date. HR conducted their harassment investigation and dismissed my complaints. They focused more on investigating me, picking my words apart, and telling me I lacked credibility and citing her with “ineffective leadership” and “poor communication.” Because of the stress caused by my supervisor, I am suffering moderate depression, anxiety, heart and liver issues. I am on FMLA since the beginning of April for these health concerns, receiving disability benefits. I am seeing a medical doctor and psychologist who have counseled me on harassment and bullying. They are recommending that i resign since the company is not making any changes for my situation, and I look for employment elsewhere. My supervisor doesn’t like me but shes made it so I can’t go to a different position either. Before I resign 6 months shy of my retirement eligibility, is there something I should be doing or considering? Do I have a case for age harassment? My supervisor did the same thing to another employee several years ago as she was eligible for retirement. That coworker resigned because she didn’t want to give the supervisor the opportunity to fire her first.